1. Field of the Invention
The present invention is an oscillation device using a quartz-crystal oscillator, and relates to a technique for compensating for aging in frequency of the quartz-crystal oscillator.
2. Description of the Related Art
A quartz-crystal oscillator has a property that a drift of oscillation frequency occurs with an elapse of driving time. Meanwhile, in the marketplace, an application in which quite high frequency stability is required to a quartz-crystal oscillator has been increasing, and normally, an OCXO is generally applied as the quartz-crystal oscillator when being incorporated in the application. The OCXO has an advantage that the drift is small, but, it is formed of a large-scale device and thus has a large power consumption. For this reason, it is considered to use a TCXO with a simple structure and small power consumption, but, the TCXO has a disadvantage that a drift amount of oscillation frequency with an elapse of driving time is large, and thus has a problem that it is difficult to be applied to an application to which high frequency stability is required.
Although Patent Document 1 describes a technique in which two quartz-crystal oscillators (quartz-crystal resonators) are structured by providing two pairs of electrodes on a common quartz-crystal piece, and by utilizing an appearance of frequency difference between the two quartz-crystal oscillators in accordance with a temperature change, a temperature compensation of oscillation frequency is conducted, it does not describe about a compensation of aging in frequency.
[Patent Document 1] Japanese Patent Application Laid-open No. 2001-292030